The invention relates to an installation for heating, ventilating and/or air conditioning the passenger compartment of a vehicle. Such an installation generally has air treatment and distribution means accommodated at least partly in a housing provided with air outlets, the de-icing air outlet and the central aeration air outlet, at least, opening into a specifically shaped upper face of the said housing and being capable of delivering treated air respectively to a de-icing vent and a central aeration vent, which are provided in a fascia of a dashboard, via ducts connecting the said outlets to the said vents, the said dashboard having an upper fascia and a front fascia.
The central aeration vent is usually situated in the front fascia of the dashboard or in the upper part of the central console, within the envelope of the driver""s arms"" reach. The space available for the central console is hence limited in height and in depth. The air passage cross-section of this vent is furthermore limited. The central aeration is therefore forced aeration, which creates turbulence in the passenger compartment owing to the high speeds of the aeration air.
International standard ISO 3958 of 15/02/1996 defines arms"" reach zones for the driver of a motor vehicle. These zones are defined as being contained within the outer envelope of two spheres defined geometrically with respect to the driver""s seat. Each sphere corresponds to the movement of one of the driver""s hands. The passenger""s arms"" reach zones can be deduced by symmetry with respect to the plane of symmetry of the passenger compartment.
The references in FIG. 10 represent the following:
Pbxe2x80x94the outer envelope of a dashboard of a motor vehicle,
Cdxe2x80x94the outer envelope of the movement of the driver""s right hand, corresponding to gripping with three fingers,
Cgxe2x80x94the outer envelope of the movement of the driver""s left hand, corresponding to gripping with three fingers,
Pgxe2x80x94the outer envelope of the movement of the passenger""s left hand, corresponding to gripping with three fingers,
Pdxe2x80x94the outer envelope of the movement of the passenger""s right hand, corresponding to gripping with three fingers,
Cgbxe2x80x94the outer envelope of the movement of the driver""s left hand, corresponding to gripping by the fingertips,
Cdbxe2x80x94the outer envelope of the movement of the driver""s right hand, corresponding to gripping by the fingertips,
Pgbxe2x80x94the outer envelope of the movement of the passenger""s left hand, corresponding to gripping by the fingertips,
Pdbxe2x80x94the outer envelope of the movement of the passenger""s right hand, corresponding to gripping by the fingertips.
These various spherical envelopes cut the outer envelope Pb of the dashboard along curvilinear lines, which divide the outer envelope Pb of the dashboard into different zones, accessible or not accessible to the fingers of one of the driver""s or passenger""s hands when gripping with three fingers or by the fingertips. These curved lines and the corresponding zones are shown in FIGS. 11a to 11g. 
The zone A1 is the part of the dashboard that lies in the intersection of the envelopes Cd and Pg.
The zone B1 is complementary to the zone A1 in the envelope Pb of the dashboard.
The zone A2 is the part of the dashboard that lies in the intersection of the envelopes Cdb and Pgb.
The zone B2 is complementary to the zone A2 in the envelope Pb of the dashboard.
The zone A3 is the part of the dashboard that lies in the junction of the envelopes Cd and Pg.
The zone B3 is complementary to the zone A3 in the envelope Pb of the dashboard.
The zone A4 is the part of the dashboard that lies in the junction of the envelopes Cd, Cg, Pd and Pg.
The zone B4 is complementary to the zone A4 in the envelope Pb of the dashboard.
The zone A5 is the part of the dashboard that lies in the junction of the envelopes Cdb and Pgb.
The zone B5 is complementary to the zone A5 in the envelope Pb of the dashboard.
The zone A6 is the part of the dashboard that lies in the junction of the envelopes Cdb, Cgb, Pdb and Pgb.
The zone B6 is complementary to the zone A6 in the envelope Pb of the dashboard.
In the definitions above, the vehicle is assumed to have a left-hand driving position. In the case of a vehicle with a right-hand driving position, the words driver and passenger merely have to be interchanged in the definitions.
The first object of the invention is to increase the space available for the console in the central zone of the dashboard.
According to one aspect of the present invention there is provided a installation for heating, ventilating and/or air conditioning the passenger compartment of a vehicle, of the type having air treatment and distribution means accommodated at least partly in a housing provided with air outlets, in particular a de-icing air outlet and a central aeration air outlet which can deliver treated air respectively to a de-icing vent and a central aeration vent, which are provided in a fascia of a dashboard, via ducts connecting the said outlets to the said vents, the said dashboard having an upper fascia and a front fascia, wherein the central aeration vent is located exclusively in the zone of the envelope of the dashboard located outside the intersection of the outer envelopes of the movement of the driver""s right hand and of the passenger""s left hand, corresponding to gripping with three fingers.
So as to further increase the regions of the dashboard which can be equipped with control knobs, the central aeration vent is positioned exclusively in one of the zones B2 to B6 defined above.
The second object of the invention is to eliminate the turbulence in the passenger compartment, especially when the device is an air conditioning device.
These objects are achieved according to the invention by the fact that the central aeration vent has a diffusing surface whose passage cross-section is at least equal to 1.5 dm2.
Advantageously, the passage cross-section of the diffusing surface is at least equal to 2.5 dm2.
According to a second characteristic of the invention, the ducts connecting the outlets of the upper face of the housing to the corresponding vents are arranged in a diffusion unit which extends transversely under the upper fascia of the dashboard, the said diffusion unit having, in its front central zone, at least one de-icing duct directed at the windscreen, and, to the rear of the de-icing duct, at least one central aeration duct produced in the form of an oblong diffusion chamber which extends transversely under the upper fascia of the dashboard.
This arrangement makes it possible to reduce the number of connecting pieces, simplify the assembly of the cockpit, and improve on the aerodynamic efficiency of the device, by reducing the pressure losses in the ducts.
Advantageously, the diffusion chamber extends transversely over the entire length of the upper fascia of the dashboard. The upper fascia of the dashboard is produced in the form of a hood, which covers the diffusion unit. This hood preferably has multiple perforations above the diffusion chamber.
Advantageously, the de-icing duct and the diffusion chamber are bounded by thin walls. The diffusion unit is preferably produced by assembling two complementary pieces moulded in thermoplastic material. The diffusion unit and the housing are fixed onto a cross-member or onto the bulkhead.
According to a first variant of the installation, the lateral aeration air outlets of the housing also open into the upper face of the said housing, the said outlets being capable of delivering treated air to the lateral aeration vents provided in the fascia of the dashboard, via lateral aeration ducts connecting the said outlets to the said vents. The said lateral aeration ducts are then advantageously arranged in the diffusion unit and extend laterally under the diffusion chamber.
Preferably, the air inlet of the lateral aeration ducts is located between the air inlets of the de-icing duct and of the diffusion chamber, and their outlets are provided in the front lateral corners of the upper fascia of the dashboard.
Advantageously, the diffusion unit is produced by assembling two complementary pieces moulded in thermoplastic material, one of the pieces being in the form of a trough having an air inlet matched to the shape of the upper face of the housing, the other piece fitting into the said trough and constituting the partitions separating the various ducts.
According to a second variant of the installation, the housing furthermore has lateral outlets for delivering air, on the one hand, to lateral aeration vents provided in a fascia of the dashboard, via lateral aeration ducts connecting the said outlets to the said vents and, on the other hand, to feet aeration vents which open into the lower zone of the passenger compartment, via lower ducts. The said lateral aeration ducts and the said lower ducts are then advantageously arranged in a lower part of the diffusion unit.
Preferably, the diffusion unit is produced by assembling two complementary pieces moulded in thermoplastic material, namely a main piece having thin walls partly bounding the ducts, and a lower cover which completes the ducts.